09/17/2008, TCRA Email Forum
Gday, I am having some trouble with a 5HP captive clutch converter in a BMW 2000 model I think, when the car is cold it runs fine, when in manual mode it runs fine, but once it is warmed up in drive I am getting a shudder in 4th gear, it feels like the lock up isn’t holding. I am using the oil that is recommended for this box. We have been using the Kevlar clutch PX-26-6 from tri components for a few years now with no trouble at all this is a first. The clutch clearance is fine and all the feed holes in the converter are fine. Any ideas as to why it would only be doing it when hot.
I suggest that you monitor the data on a scan tool to see what the converter is actually doing. I am a bit vague on the BMW but the Audi with same transmission is prone to shuddering during the regulation phase. If you say that you have had success with these in the past then it is unlikely that it is a lining issue. You may also care to read the newsletter article at https://www.tcraonline.com/images/newsletter/2008_06_newsletter.pdf This is a personal experience for me! Other issues that we have had transmission wise with these are valve body wear, solenoid problems and of course engine issues that are not the converter at all. Post the actual transmission code from the plate on the side and I may be able to be of more help.
If this unit is doing it hot, this means only when the fluid gets thin. Sounds like an internal leak, I would check the viton and seal and the piston journal where the viton rides! Good Luck!
Thanks to Martin and peter for your responses. We are going to try the red material and see how it goes. One thing I have noticed that is different between an OEm converter and our converter after it is welded up is that ours isn’t as hard to turn as an original unit. By this I mean if you put the turbine into the front cover it takes a lot more force to turn an original one than ours. Does anyone know how tight these lock up plates need to be, is there a point if they are too loose that it might not work properly
I would be very careful using the red material. Much better to use one of the materials that were suggested to you earlier. I will pass your other question on to my technicians and get back to you.
We had this problem with a small number (5%) of 5HP24 a couple of years ago – mostly Jags, but a couple of BMW. We never really got to the bottom of it – the only thing we found was the PX-26-6 was slightly varied in friction thickness – the maximum we found was 0.008″ difference, but normally 0.004″ or so. It seemed very unlikely to us – but could it be enough to engage slightly unevenly and cause judder? We have used the Sonnax / Alto plate FS-CP-3 / 132714 since, and made no other change to build procedure and not had another problem, for well over a year. You say you are using the correct oil (Esso LT71141) – are you also rebuilding the transmission? We sell our converters to rebuilders – we always put a small amount of the correct oil in – but what the transmission rebuild shop does is another matter!! We can only warn them and let them know there is no warranty if they use the wrong oil. In a couple of the judder problems we came across they had used Dexron.
We also pre soak the plates before fitting.
If the plate is easy to turn after fitting in position this could also be part of the problem. In our experience they should be difficult to turn – to the extent that you need to blow an airline into the centre, to allow them to centre to fit the turbine in place. We always reweld / retab the plate cover under pressure – in a press – to make sure they are fully down. I think Joe mentioned “backing off” this pressure in one of his articles – but we have never done this.
I assume these lock ups are applied until pressure releases them – if they are very loose this means they aren’t ever fully applied, which could cause a judder?
Have you had to machine the cover on the friction surface land area (due to plate running metal to metal when failed)? We have never had a problem when having to do this – but I assume taking too much material off will allow too much clearance and the plate not engaging properly? Hope these are of some help.
It is not built right you should make a tool to put a torque wrench in the spline and it should hold 73 inch lbs.
Here is the reply from Bob Ryan who is in my converter department Martin Luca If you keep the retaining plate in its original position, you should have no problems. Those three straps are just that “driving straps” rather than springs. Its only because they are made of hardened steel that they give the impression of being springs. No worries on the amount of perceived drag on the friction plate as long as you don’t position the plate higher than it was in the first place.
Hello to all, The “driving straps” that Bob Ryan is referring to are only there to keep the piston rotating with the cover in a manner that will not create a noise. Hydraulically the piston would apply and release whether they were there or not. Keep in mind that when the retainer that secures the “driving straps” to the cover is attached to the cover the piston only has .040″ of available travel. You must keep the clutch release clearance as close to .010″ as possible for the clutch to apply properly. Ed
Another reply from Bob In addition to what Ed has stated, you need to realise that those straps are flexible levers (Not too flexible) therefore they will mechanically restrict the movement of the piston if not placed correctly in relation to the front cover. If you need to machine the front cover you should remove a like amount from the boss the friction welded plate mates with, keeping the geometry as intended.
You write … We always reweld / retab the plate cover under pressure – in a press – to make sure they are fully down. I think Joe mentioned “backing off” this pressure in one of his articles but we have never done this. I don’t ever remember writing about Backing off. That might have been Ed’s article. We do the same thing as you and keep it in a press. I will mention that we have gone to a high carbon clutch in these application with MUCH BETTER success Please keep in mind the clutch strategy which is to slip the clutch. We are seeing that clutch material and compatibility is CRITICAL in later model vehicles with PWM clutch apply strategy
Apologies Joe, It may have been another article – I know there were 2 or 3 of these articles in quick succession – or it may even have been mentioned by someone at a seminar? I agree about the material in later applications – I am pretty sure the Sonnax plate FS-CP-3 is paper? But must admit we have had 100% success with it over the last 18 months. Maybe Ed can let us know. I believe that the plate they are bringing out for the 6HP has a high carbon type friction?